Ross, Julie A.; Davies, Stella M.; Potter, John D.; Robison, Leslie L.; Ross Julie A.; Department of Pediatrics, University of Minnesota; Division of Epidemiology, School of Public Health, University of Minnesota; Davies Stella M.; Department of Pediatrics, University of Minnesota; Potter John D.; Division of Epidemiology, School of Public Health, University of Minnesota; Robison Leslie L.; Department of Pediatrics, University of Minnesota; Division of Epidemiology, School of Public Health, University of Minnesota